Supermarket chain Kroger is recalling ten-ounce packages of Fresh Selections spinach that have a "best if used by" date of September 16, 2012. Testing revealed the product may contain Listeria monocytogenes bacteria, which if eaten can lead to a severe illness called listeriosis, reports CBS News.

Healthy people who eat the bacteria may not get sick, but the elderly, women who are pregnant, or people who have a weakened immune system are especially at risk for illness. Listeria ingestion can cause fever and muscle aches, often with other gastrointestinal symptoms.